Safety control for hoists and circuit therefor



Sept.' 17; 194e. H, F, VICKERS A 2,407,693"

SAFETY vCONTROL FOR HOISTS AND CIRCUIT THEREFOR Filed Dec. 3, 1936 3Sheets-Sheet 1 @QQ ,if

E( ATTORNEYS.

Sept. i7, 1946. H. F. vlcKERs SAFETY CONTROL FOR HOISTS AND CIRCUITTHEREFOR Filed Deo. 3, 1936 3 Sheets-sheet 2 @w .www

ATTORNEYS Sept. 17, 1946. H-.F. vlcKERs f' 2,407,693k

SAFETY CONTROL FOR HOISTS AND CIRCUIT THEREFOR ATTORNEYS.

Patented Sept. 17, 1946 "SAFETY CONTROL FOR HOISTS `ANI) CIRCUITTHEREFOR Harry F. Vickers, Detroit, Mich., assignor to VickersIncorporated, Detroit, Mich., a corporation of -Michigan "ApplicationDecember 3, 1936, Serial No. 114,008

(Cl. A198--37) 15 Claims. 1

This'device concerns 'a safety control for hoists vand circuit therefor,and has to do particularly with a hoist adapted to convey articles fromone station to another and means for controlling the movement of saidhoist in either direction between the said stations.

The present device operates by means of a chain type conveyerhydraulically driven and supplemented by a system of controlsbothhydraulic and electric, which is believed to be a new idea, whenconsidered together with the safety locking device.

An object of this invention -is to provide an automatic control ofstarting, stopping and direction of travel, when cert-ain requirementsof these functions are to be riuliilled, `said control being practicallyTree of 4any parts that are `apt to get out 4of order or lackdependability in operation.

Other objects will be apparent from the `following description andclaims when considered together with the accompanying drawings.

In the drawings:

Fig. `1 is a new chart largely diagrammatic. of a chain type hoist andcircuit therefor, with the control valves in section, and showing therelative position oi valves at the iirst stage of operation or with bothstations loaded.

Fig. la is a diagrammatic illustration of the hoist showing bothstations loaded and the relative position of the switches.

Fig, 2 is a view similar to Fig. l., showing the relative position ofparts `during the second stage of operation, or with the lower stationempty.

. Fig. '2a is a view similar to Fig. la showing the lower station empty'and the'upper station. loaded.

Fig. 3 is aview similar to Fig. l but illustrating the position ofvarious parts and operation of circuit during the downward motion of theconveyor, both stations being empty and the article in transit,

Fig. 3a is a view similar to Figs. la and 2c showing both stationsunloaded and a projectile in transit.

The illustrated embodiment of this invention includes, a deliverystation X which may be termed an upper station, a loading or lowerstation Y, and a chain type conveyor diagrammatically illustrated by thedotted line Z and operatively connected to a hydraulic motordiagrammatically illustrated as at H. The conveyor Z which may be anykind of an endless conveyor unit, is adapted to be actuatedsimultaneously with the shaftl?, one end of which is operativelyconnected to a hydraulic motor H and the other cnd to an automaticcontrol unit generally designated U; in other words, the drive isusually from the hydraulic motor H through suitable reduction gearing tothe conveyor .Z and to the control shaft T. The unit U also includes alatch and cam mechanism operatively connected with valve mechanisms forcontrolling the step by step movement ofthe conveyor, including adirectional stop control D. The endless conveyor unit above referred tois illustrated and described in detail in my copending application,Serial N o.

` stemmed Aug, 10, 1935.

Fluid under pressure is supplied by a pump I, of the constantdisplacementtype, supplying fluid from tank reservoir Z Linder pressureto conduit 3. The pressure in conduit 3 is limited by vented reliefvalve il which operates in the following manner: Through small orince 5in piston 5a the pressure inconduit 3 is transferred to chamber causinga balance between the said chambers. With spring l set to an initialpressure of approximately 20# per square inch, the resulting pressure'to the left of piston 5a, las viewed in the drawings, is approximately2G# per square inch more than the normal operating pressure in chamber 6and conduit 3. This pressure to the leit of the valve urges it to closedposition. The maximum relief pressure is controlled by an emergencyrelief valve', which by the `adjustment of the spring limits thepressure in chamber 6. If venting line 9 is connected to the tank roratmosphere, this removes the effect of pressure in chamber E, causingthe pressure in conduit 3 to fall to the pressure as limited by spring'l which is still acting o-n the piston.

On diametrically opposite sides `of the automatic control unit U arelocated a cam lever a and a latch b and auxiliary control piston valvesA and B. The cam operated accelerationdeceleration valve A is on theleft hand side of the automatic control unit, as in Fig. l; and thelatch operated valve B is 'on the right siede of the automatic controlunit. The valve B is connected by conduits to a solenoid operatedstarting valve C which is connected by conduit 3 to the pressure iiuidthrough the vented relief valve 4. VThe directional valve D is connectedthrough conduits I3 and i9 to the hydraulic motor H to control thedirection of movement of the hoist. The above mentioned valves A, B, Cand D Vhave intercommunicating connections. for reception of a pressurefluid, and for actuation of the conveyor when certain conditions exist.

To better understand the operation of the circuit and control of theconveyor motor it is thought best to set forth the primary conditionsdesirable for obtaining automatic control in a predetermined direction,as follows:

(1) With the upper station iilled, and lthe knob of directional valve Dset to lowering position,

Vthe conveyor Z should` move downward only when the lower station Y isempty.

(2) With both upper and lower statioinsX and Y mity. it is importantthat nio motion of the conveyor should ensue irrespective of the settingdo; of the kno-b of directional control valve D.

(3) With both stations lled, as shown in Fig. 1.a, it is important thatno motion shall ensue, irrespective of the setting of the directionalcontrol valve D.

(4) With the upper station empty and the directional control valve D setto hoist the motion should be upward only when the lower station isfilled.

The preferred means for deriving the required results when any of theabove listed conditions are met with, is what is commonly called a threepoint electric control circuit, embodying 'two two-way article sensitivelimit switches S1 and S3 interposed by a four-way switch Sz, as will besubsequently described. The switches S1 and S3 are so positionedadjacent the stations X and Y as to be actuated or released by thepresence or absence of articles at the respective stations.

Figs. 1 and la illustrate the third condition of operation, the upperstation switch S1, being correspondingly set for a filled condition. The

' trol valve A precedes the shift of S1.

intermediate four-way switch S2 is attached to the directional controlvalve D to eifect a transposition of control wires E1 and E2 wheneverthe directional control valve D is shifted. With s the lower stationtwo-way switch S3 set to a lled position, the electrical circuit line Eaand E4 is opened causing a solenoid E5 to be ineffective. With theValves-B and C of Fig. 1 in the inactive position, the venting line 9through the corresponding ports is opened to the tank through thechannels 9, Ill and II allowing the described -fall in pressure, bymeans of the vented relief valve 4.

Figs. 2 and 2a illustrate the iirst condition of f operation, theswitches S1, Sz and S3 being so interconnected as to magneticallyactuate the valve C. With the knob of directional control valve D set tolower, the movement of starting valve C vto the left causes thefollowing consecutive functions. Fluid flow through the venting line 9is cut ofi by closing ports 36 and 31 allowing the pressure in conduit 3to build up to the required resistance. By this movement of the valve Cthe pressure conduit 3 is opened through a conduit I2 to port I3 ofvalve B and with a clear channel to port I4 and conduit I5. With thedirectional control valve D in the position shown in Fig. 2,

rconduit I5 is connected through ports I6 and I1 with a lower setting ofthe directional valve D, and finally through the conduit I8 to tend todrive the motor momentarily in a lifting direction. At this describedposition of the valve D the return uid is directed from channel I9through the open ports 2U, 2I toI conduit 22 through port 23, and openport 24, which finally connects to the conduit I I, a tank connection.

Pressure in the conduit I5 is maintained to the required value by thespring loaded check valve `25, the function of which will besubsequently def scribed mo-re in detail. By a further movement ofstarting valve C, pressure conduit 3, through portl 26 and conduit 21,applies pressure to chamber 28, effecting a withdrawal of the motorholding latch b. This withdrawal o-ccurs during the momentary liftingmovement of the motor.

With the withdrawal of the latch b and attached valve B, the conduit 22is diverted from the tank port 24 to the pressure conduit 29, effectinga reversal of the fluid flow to the motor, (see the position of valve Bin Fig. 3).

Momentarily after the valve B is moved to the right (as in Fig. 3), thestarting valve C still remains to the left as shown in Fig. 2, allowinga clear channel for the return fluid from the llfQlQr through the lineI8, ports I1 and I6 to the spring loaded back pressure valve 25, whichoffers a back pressure to the return flow ofthe motor to preventover-run when lowering. From the spring loaded valve 25, the return uidhas free access to the tank through conduit 33 and ports 3l and II.

Now after motion has started in the downward direction, as shown in Fig.3a, the upper article, being in transit, allows movement of switch S1 byreason of its spring 32 to divert the electrical ow of current from lineE2 to E1, thereby de-energizing solenoid E5 and allowing starting valveC to return to normal as indicated. The member i: U is provided with acam lobe a; the timing of the cam lobe a', actuating valve A, and theshifting of the electrical switch Si, are so arranged. that a movementto the right of auxiliary con- The purpose of this timing relationship,or lost motion, is to allo-w a continued free flow of the return fluidfrom the motor before the valve C returns to normal. With the lobe ofthe cam beyond the roller of valve A, spring 33 forces valve A to theright as limited by the dwell on the cam as shown. With the valve A inthis position the return fluid from the motor is directed from theconduit 30 to the ports 34 and 35 to the tank conduit II. By

Vreason of the venting ports 36 and 31 of valve C and ports I and 24being connected in series,

venting of the relief valve is prevented and pressure maintained by theclosure to port 24, regardless of the return of Valve C. With the returnof the valve C to normal the port 25 is diverted to conduit II, a tankconnection, allowing spring 38 to hold the latch against the peripheryof the notch plate, preparatory to its nal mating with the notch at thetermination of the cycle to lock the motor M against further movement.With the latch dwelling on the periphery of the said cam plate, thevalve B still maintains open channels between the ports 29 and 23 andthe necessary closure of conduit I3 to port I4, allowing a continuationof the downward motion of travel. The venting line 9 at the referredposition o-f the valve is still obstructed by the closure of ports IIland 24.

Nearing the completion of the cycle or the termination of the downwardmovement, the timing of the cam lobe a' with reference to valve A is inadvance of the iinal notching'of the latch b for the purpose ofmaintaining motion to the ultimate destination before conduit 9 is nallyvented to the tank.

In movingV to the left by the action of the cam lobe, valve A graduallyretards the flow from ports 34 to 35 by the metering action of a taperedvalve portion 33. After complete closurel ofthe ports 34 and 35, motionto a lesser degree is still continued by a needle valve 4u, which shuntsthe aforementioned ports and allows a restricted volurne to iiow fromconduit 3i] to II. After slight continued motion the latch. b is allowedto drop into the notch of the cam plate to lock the motor M againstfurther movement, causing the valve B to move further to the leftfinally opening the venting line 9 through the ports Il) and 24 to thetank conduit II. In addition the conduit 22 is connected by reason ofthe ports 23 and 24 through the `tank conduit II, preparatory for thenext cycle. Coupled with the timing relationship `iust described, theswitches Si and S3 again as'- sume the position as indicated by theloading c-ondition at that moment, as in Fig. la.

As previously mentioned the additional purpose ywould. :be -adequateAfor the `desired results. elongated -slot :4l in the `member .forminglobe It is .assumed Yin this circuit that the back pres- .sure setting:of the valve 25 is of sufficient value to .slightly raise or.sufficiently relieve 'the load `'of the conveyor to .facilitatewithdrawal `of the latch. ,It will 'be noted that with an .insuicientipressure setting .of the valve 25 the iiuid 4for Amomentary raisingwould `lay-pass from conduit I5 to `conduit 3.8. :By `reason of thefact-that the `pressuresetting of valve must be suicient to properlycompensate "for the'unbalanced load, it 'fis logical toassume that aslightly higher value `n a is provided to permit adjustment betweenlobea .and the notchof cam U..

In operation, from the previously mentioned four possible sets ofconditionsexisting at .the loading stations, and the correspondingsetting of the safety electrical switches Si and Sa, it will be seenthat it is impossible to actua-te the hoist 'until -the article at thedelivery station has .been

removed. This will :prevent the article at .the

-delivery station from being carried on around the conveyor and possiblydamaged, or if it should be `an `explosive such as a can ofnitro-glycerine, it will prevent .the movement to .any .other undesiredor dangerous position. Any standard mechanism can .be iutilizedforeiecting .this automatic stop, and Aone .possible .structure .isshown in all the drawings as `being .a solenoid, operated by twotwo-point switches .interposed by a four-way switch.

When the motor .is to .be moved in a .hoisting direction, thedirectional valve TD is .shifted from its position as shown to aposition connecting line 22 with line ll. AS .soon as auxiliary controlvalve B is .shifted .by pressure from valve C to the position shown inFig. 3, pressure from 4line 3 will .eiect a .hoisting .movement of themotor. This will continue until latch l) drops in cam U to close line 3from-line 122.

From the present disclosure lit will thus be seen there has not onlybeen produced .a combination of station controls and cooperating valvecontrols suitable for the safe conveying .of articles, but a mechanismthat contains a minimum .number of parts that might be apt to .requireattenn tion or replacement.

What I claim is:

l. In a .hydraulic .actuating and control system for controlling themovements of an endless conveyor vextending' between spaced loading anddelivery stations, a conveyor, a pressure source, a reversible Aconveyor.motor having two ports interchangeable as pressure-exhaust ports,directional valve means for selectively directing liquid under pressureto said motor parts, a series of hydraulic conduits connecting .saidpressure source and said directional valve means, means for limiting thepressure in .said conduits, a starting valve in said .conduits adaptedin one position to block flow of pressureliquid from ,said source `and.in another position to passliquid from `said source to said.directional valve means, an `actuating `means for said starting valve,article responsive means `at `each of said stations to be influenced bythe presence -of an article at said 'stations and means operativelyconnecting .said

the station toward which the conveyor will move -is emptyand thestation. from which the conveyor will move is loaded, ,a .locking wheeloperatively connected to said motor, .a latch for engaging :said 'wheelt'o lock said motor, and .means .con- `.n'ec'ted `to Vsaid .latch .and.operated by pressure `directed from said .starting valve lfor.disengaging l said latch :from said wheel to .permit operation.of'lsaid motor, .said 'starting valve 'being ar- `ranged 'to directliquid .under pressure to operate said latch mean-s .only when said:starting valve .iss'hifted fromlit's `blocking position.

2. Inzahydraulic actuating and .control-system for controlling themovements :of anendless lcon-- veyor hoist, .extending .between spacedloading @and .delivery stations, a 'pressure source, a 1re versibleconveyor :motor having ports intertchangeable .as :pressure-exhaust'.ports. .directional valve means .for selectively `.directing liquid`under ,pressure to'saidmotor Yports to cause hoisting or lowering:act-ion, hydraulic conduits connecting said `pressure source .and saiddirectional lvalve means, Va starting valve inzfsaid conduits adapted,in one position, -tjo `blc-cl: .flow of :pressure liquid from saidsource and, in another position, topass :liquid from said source to saiddirectional valve means, ya locking wheel operatively connected Ito`said motor, .a latch forengaging said wheel to lock said Amotor againsta `downward movement, lmeans connected .to said latch and operable bypressure directed from `the source through said starting valve for-disengag-ing said latch `from said wheel, and `a valve in said`conduits between the starting valve .and the directional valveyopferable with said last named means and .adapted to direct liftingpressure momentarily to said motor .through said directional valve topermit withdrawal of :said latch from said wheel and to direct pressunethereafter to said motor through said `directional valve to eiectlowering action, said starting valvebeing arranged to'direct liquidunder pressure to operate said latch means only when .said star-tingvalve is shifted from its blocking position.

'.3. In ,a hydraulic actuating and control system 'for controlling 'themovements of .an endless hoist conveyor extending 'between spaced upper.and 'lower loading and delivery stations, a pressure source, `areversible hydraulic conveyor motor having two `ports interchangeable aspressure and exhaust ports, .a .directional valve means, an .auxiliary.control valve, supply .and return conduits .connecting said directionalvalve with said motor. and with said auxiliary control Valve, saidconduits .to .be used interchangeably as `pressure and Aexhaustconduits, a .tank conduit leading from said directional control, astarting valve, conduits connecting said starting valve with .saidpressure source and with said auxiliary control valve, said startingvalve being adapted in oneposition to block flow of pressure liquid fromvsaid sourceand in another position to pass liquid from said vsource tosaid auxiliary valve to actuate the same, said auxiliary 'valve beingadapted in one position, to pass liquid under pressure Ito one of Vsaid.conduits leading .to the directional `valvel and 1in another :positionto pass pressure liquid tothe other :of 4.said conduits leading to saiddirectional valve, locking means operably connected with said motor toprevent lowering, and means for .disengagng said lock-ing means, saidvalves cooperating to effect .momentary 4lifting action ofsaildlconveyor motor to permit disengaging of said latch, .and to effectthereafter a lowering action .of .said motor,

4. In ahydraulic actuating and control system for controlling themovements of an endless conveyor hoist extending between spaced upperand Vlower loading and delivery stations, a pressure source, areversible conveyor motor having one port to be used as a pressure portfor hoisting and as an exhaust port for lowering, and a second port tobe used as a pressure port for lowering and as an exhaust port forhoisting, a locking means comprising a movable part operativelyconnected with said motor, and a movable latch for engaging said movablepart to lock the same against movement, means for withdrawing saidlatch, and valve means to be automatically actuated at the start o'f alowering movement for momentarily directing liquid under pressure to thehoist pressure port of said motor to permit withdrawal of said latch andthereafter directing pressure to said lower pressure port.

5. In a hydraulic actuating and control system for controlling themovements of an endless conveyo1` hoist extending between spaced upperand lower loading and delivery stations, a reversible motor to serve asa power unit for said hoist, a releasable holding means for said motor,means for releasing said holding means, directional and starting meansresponsive to load conditions, for controlling the movement of saidmotor, and means responsive to said directional and starting means forcausing a momentary hoisting action of said motor before a loweringaction to permit release of said holding means.

6. In a hydraulic `actuating and control system for controlling themovements of an endless conveyor hoist extending between spaced upperand lower loading and delivery stations, a pressure source, a hydraulicmotor having one port to be used as a pressure port for hoisting and anexhaust port for lowering, and a second port to be used as pressure portfor lowering and an exhaust port for hoisting, an auxiliary controlvalve, hydraulic connections between said valve and said pressuresource, two conduit lines connecting said auxiliary valve with saidmotor ports, a directional valve in said two lines adapted in oneposition to open each of said motor ports, respectively, to a connectingline leading to the auxiliary control valve, and in another position toopen one of said lines to the pressure lowering motor port, a lockingmeans for said conveyor comprising a movable part and a latch forengaging said movable part, said auxiliary control valve being adaptedin one position to direct pressure through one of said lines to thepressure hoisting port of said motor to effect momentary liftingmovement to permit release of said latch means, and in another position,to effect lowering of said hoist, and means to effect shifting of saidauxiliary valve.

'7. In a hydraulic actuating and control system for controlling themovements of an endless conveyor hoist extending between spaced upperand lower loading and delivery stations, a pressure source, a hydraulicmotor having one port to be used as a pressure port for hoisting and anexhaust port for lowering, and a second port to be used as a pressureport for lowering and an exhaust port for hoisting, an auxiliary controlvalve, hydraulic connections between said valve and said pressuresource, two conduit lines connecting said auxiliary valve with saidmotor ports, a directional valve in said two lines adapted in one Yiliary control valve, and in anotherY positionto open one of saidlinesto the pressure lowering motor port, a locking means for said conveyorcomprising a movable part and a latch for engaging said movable part,said auxiliary control valve being adapted in one position to directpressure through one of said lines to the pressure hoisting port of saidmotor to effect momentary lifting movement to permit release of saidlatch means, and in another posi-tion, to effect lowering of said hoist,and a starting control valve in said system adapted in one position toblock flow of pressure liquid from said source, and in a second positionto pass pressureliquid from said source to said auxiliary valve to shiftthe same from the momentary lifting position to a pressure loweringposition.

8. In a hydraulic actuating and control system for controlling themovements of an endless conveyor extending between spaced loadingstations, a liquid supply tank, a pressure source, a conveyor motor,lines between said motor and said pressuresource, a starting controlvalve in said lines, an auxiliary line between said valve and said tank,and a relief valve connected to said lines between said starting controlvalve and said pressure source, said relief valve comprising a housingprovided with a cylinder connected at one end by said lines to thepressure source and to the tank and connected at a second end by saidlines to said starting control valve, a piston shiftable in saidcylinder having a restricted passageway therethrough andV means thereonfor normally blocking the tank connection of the cylinder, said startingcontrol valve being adapted in one position to permit flow of pressureliquid from the source to said motor and to close said second end of therelief valve cylinder from the tank, and in a second position to blockow of pressure liquid from the pressure source and to open the secondend of the relief valve cylinder to the tank, whereby pressure liquidfrom the pressure source may actuate said relief valve piston to openthe tank connection of the cylinder and bypass the pressure flow, meansassociated with said motor for controlling the directionof movementthereof, and auxiliary means associated with and responsive to movementof said starting valve for directing liquid under pressure momentarilyto drive said motor in one direction immediately prior to prolongedmovement in the other direction.

9. In a hydraulic actuating and control system for controlling themovements of an endless conveyor hoist extending between spaced loadingstations, a liquid supply tank, a pressure source, a conveyor motor,directional means associated with said motor movable to a lifting orlowering position for controlling the direction of movement thereof, anauxiliary contro1 valve, a starting valve, lines connecting said valves,pressure source and directional means, said valves being arranged tocooperate in one position to block pressure flow from said source tosaid directional means, and each being movable to a second position topermit flow through said lines to cause a momentary lifting movement anda prolonged lowering movement of said motor when said directionalmeansis set for lowering movement and a prolonged lifting movement when saiddirectional means is set for lifting movement.

l0. In a hydraulic actuating and control system for controlling themovements of an endless conveyor hoist extending between spaced loadingstations, a liquid supply tank, a pressure source, a conveyor motor,directional means associated with said motor movable to a lifting orlowering position for controlling the direction of movement thereof, anauxiliary control valve, a starting valve, lines connecting said valves,pressure source and directional means, said valves being arranged tocooperate in one position to block pressure flow from said source tosaid directional means, and each being movable to a second position topermit ilow through said lines to cause a momentary lifting movement anda prolonged lowering movement of said motor when said directional meansis set for lowering movement and a prolonged lifting movement when saiddirectional means is set for lifting movement, a relief valve in saidlines normally maintained in closed position by pressure, said startingand auxiliary control valves being adapted to control the pressureclosing said relief valve whereby said relief valve will remain openuntil said starting valve is shifted.

11. In a hydraulic actuating and control systern for controlling themovements of an endless conveyor hoist extending between spaced loadingstations, a liquid supply tank, a reversible conveyor motor, a pump, ahydraulic control circuit for directing pressure from said pump to saidInotor, and means for controlling the speed of said motor atpredetermined times in the cycle of movement of said conveyor comprisinga deceleration valve adapted in one position to pass exhaust liquid fromsaid motor to the tank, and means responsive to the movement of saidmotor for shifting said valve to cut off gradually the exhaust flow tothe tank, and a second valve means located in parallel with saiddeceleration valve and adapted to further restrict the flow of exhaustliquid upon the shifting of said deceleration Valve.

l2. In a hydraulic actuating and control system for controlling themovements of an endless conveyor extending between spaced loadingstations, a pressure source, a conveyor motor, directional meansassociated with said motor to control the direction of movement thereof,a starting valve, an auxiliary control valve, lines connecting saidvalves, pressure source, and directional means, said starting valvebeing adapted to be momentarily shifted in response to certain loadconditions at said stations to direct pressure from said source to saidauxiliary control valve to shift the same, means for maintaining saidcontrol valve in shifted position for a predetermined movement of saidmotor, said control valve being adapted, when in one position, to directpressure from said starting valve to said directional means to eectmomentary movement of said motor in one direction, and, when shifted, todirect pressure from said source to said directional means to effectprolonged movement of said motor in the other direction.

13. In a hydraulic actuating and control system for controlling themovements of an endless conveyor extending between spaced loadingstations, a pressure source, a conveyor motor, directional meansassociated With said motor, to control the direction of movementthereof, a starting valve, an auxiliary control valve, lines connectingsaid valves, pressure source, and directional means, a p-ressurecontrolled relief valve in said lines associated .with said startingvalve, said starting valve being adapted to be momentarily shifted inresponse to certain load conditions at said stations to direct pressurefrom said source to said auxiliary control valve to shift the same andto effect closing of said relief valve, means for maintaining saidcontrol valve in shifted position for a predetermined movement of saidmotor, said control valve being adapted, when in one position, to directpressure from said starting valve to said directional means to effectmomentary movement of said motor in one direction, and, when shifted, todirect pressure from said source to said directional means to effectprolonged movement of said motor in the other direction.

14. In a hydraulic actuating and control system for controlling themovements of an endless conveyor extending between spaced loadingstations, a pressure source, a conveyor motor, directional meansassociated with said motor to control the direction of movement thereof,a starting valve, an auxiliary control valve, lines connecting saidvalves, pressure source, and directional means, said starting valvebeing adapted to be momentarily shifted in response to certain loadconditions at said stations to direct pres-V sure from said source tosaid auxiliary control valve to shift the same, means for maintainingsaid control valve in shifted position for a predetermined movement ofsaid motor, said control valve being adapted, when in one position, todirect pressure from said starting valve to said directional means toeffect momentary movement of said motor in one direction, and, whenshifted, to direct pressure from said source to said directional meansto effect prolonged movement of said motor in the other direction, andvalve means for controlling the pressure utilized for said momentarylifting.

l5. In a hydraulic actuating and control system for controlling themovements of an. endless conveyor extending between spaced loadingstations, a supply tank, a pump, a supply line leading from said pump, arelief valve in said supply line comprising a `piston valve for closingsaid supply line from the tank and a pressure chamber behind said valvefor holding it in closed position, a starting valve and an auxiliaryvalve,

each connected to said supply line, a conveyor motor to be operated bypressure from said pump, receiving lines connecting said auxiliarycontrol valve and said motor, a directional valve in said receivinglines for directing pressure to and from said motor, said starting valvebeing adapted in one position to connect said relief valve pressurechamber through said auxiliary control valve to the tank and to blockflow from the supply line leading thereto and being shiftable to asecond position to close said relief valve pressure chamber, and to opensaid supply line to a receiving line through said auxiliary controlvalve and to direct pressure to said auxiliary control valve to shiftthe same, said auxiliary control valve being adapted in one position toblock the supply line leading thereto and to pass pressure ow from thestarting valve to a receiving line to effect momentary movement of saidmotor in one direction, and being shiftable by pressure from saidstarting valve to a seco-nd position in which said supply line is opendirectly to another of said receiving lines to effect a movement of saidmotor in the other direction, and in which said relief valve pressurechamber is closed, and means responsive to movement of said motor formaintaining said auxiliary control valve in said second position for apredetermined movement of said motor.

HARRY F. VICKERS,

